some help with protections of a syncronous generator 1

[mottt]

hi I got a 1950 Siemens AC syncronous generator, 700 kW, and I´m going to retrofit excitation... the idea is to connect a DSR 100 Basler regulator, to feed the excitation on the main rotor... and use a GE multiline for protections.
But I´ll like to ask you some questions about this generator, or other old generators...

1.- Excitation time? or how to calculate it?
2.- Maximum capacitive reactive current? I mean how far I can go into power factor capacitive seeing it from machine side?
3.- Reverse power when the prime mover is a turbine (francis) ??
4.- Over load? how much time?
5.- Negative sequence? how much time?
6.- Zero sequence?? how much time?
I´m just asking for your usual numbers?? or if you got experience with older machines like this one...

thank and hope you´ll find interesting this threat

 

[Skogsgurra]

Dear motorexplosion,

I have watched your questions for some time now. It seems that you are trying to do things that you should let a trained person do. You cannot do the kind of work that you are trying to do without knowing the hows the whats and the whys.

I am worried. Please do get a properly trained person to help you. There are very high power levels involved and you need to know exactly what to do. Or your handle will become more real than any of us wants it to be.

I consider myself rather well informed in many fields of electricity and electronics. But I would not do what you try to do. I would get a professional - someone that does this kind of work daily or at least montly - to do the job.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[TheBlacksmith]

I've got to side with Skogs on this one. A amn has got to know his limitations. Basler has a lot of trained sales engineers that could analyze your requirments and provide safe workable solutions. Might cost a few dollars; more than zero and a lot less than a serious injury or a repalcement generator.

 

[mottt]

I have worked with Basler equipment for several years, and know exactly how to configure the excitation system but i got some doubts about the protections... specially relative to the old machines, cause i have done commisioning of modern generators, with basle DEC 200 or 300, and with ABB unitrol F, but I ignore..things like:
1.- Excitation time? or how to calculate it?
Normally I use to desexcite the generator without load, and with a oscilloscope read the time to get into remanent voltage, but I´m not sure if it´s the same for the older mica asphalt generators.

2.- Maximum capacitive reactive current? I mean how far I can go into power factor capacitive seeing it from machine side?
The machine have no name plate, and I don´t know the power factor that´s usual on this old machines....

3.- Reverse power when the prime mover is a turbine (francis) ?? on diesel groups I use to adjust the 5% of the nominal power...
4.- Over load? how much time? I´m just asking, cause this is not my thing... I´ll use a GE multiline system, but i´ll use a commisioning enginier of protections, just wonder the valiums for an older machine... in a modern no problem, but i´m asking myself if the fact the machine is an older machine...insted it´s isolation and polarization index is ok, if we have to take care, and be more conservative in the numbers??
5.- Negative sequence? how much time? The same i´m just asking if someone will know or can give an idea of the normal values of negative sequence in an old machine.

6.- Zero sequence?? how much time? The same as above.

I´m a little worried, cause I´m very experienced into configuration of Basler equipments (digital regulators) I go to differents training courses.. but normal work for me is new and modern machines... never have been working with old one machines... and the same for the GE guy, for this i ask for help... cause i´ll like to give this guy a point of view more far away of the typical values for modern machines.....
I don´t know that kind of people with such experience, here when I ussually paid a lot of money for an engineer, use to come a young guy, that don´t know more than me or other guys of my company.... maybe there in the United States or other places but not here.... and in other hand... a 700 kw machine won´t give so much money to pay for a expensive technician... from other country...
take care and hope you could help`me....

 

[Skogsgurra]

OK. You have the knowledge and experience. Then I do not quite understand why you ask those rather basic questions here.

Some of your questions can be answered by looking at the capability curve. And, if there isn't one (no name-plate you say), it is difficult for anyone to anser your questions better than you can yourself. We don't even know the make and speed of this machine. There must be a manufacturer somewhere that can answer your questions or that has experience with similar machines.

Can't believe that you are trying to guess - let alone trying to make us guess - data for a machine without a name-plate.

Other questions, like reverse power and zero sequence as well as overload time constant are more or less something that you have to decide yourself. A low RPM machine can have a time constant of a couple of hours while a fast machine 3000 or 3600 RPM may be around 30 minutes. Do you really have to have the exact value? Use 15 minutes. That will probably be a safe value. It will not let you overload the machine for very long time. But are you really planning to overload it for any length of time?

We are a helpful bunch here. But sometimes we think that the best help is specialist hands-on - especially when dealing with power equipment.

I can agree that 700 kW isn't an extremely high powered machine. But power enough to create bad accidents if not handled right.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[waross]

A note on the power factor rating of a generator.
First generators by themselves are rated by KVA. Volts is the rated voltage. Amps is the rated amperage. If you change the operating voltage, for instance from 240 volts to 208 volts, the safe KVA rating will drop to reflect the change in voltage. (Yes, in some parts of the world 240 volts and 208 volts are both common three phase voltages.)
The KW output of a generator set is determined by the power of the prime mover.
The power factor of a generator set is the ratio of the prime mover output power in Kilo-Watts to the Kilo-Volt-Amp rating of the generator end.
As an example:
Consider a generator set rated at 100 KVA, 240 volts, 0.8 PF. We may assume that the prime mover will output 100 KVA x 0.8 PF = 80 KW (Plus a small amount for losses.
The voltage of the set is now adjusted down to 208 volts.
The safe KVA is now 100 KVA x 208 V / 240 V = 87 KVA.
The prime mover is still outputting 80+ KW. The new power factor is 80 KW / 87 KVA = 0.92 PF.
Your actual power factor will be determined by the load.
It will be the cosine of the angle by which the current lags (or leads) the voltage.
Your power factor rating will be determined by the
ratio of the power output of the prime mover to the KVA of the generator.
In the case of conversion from three phase to single phase, as is common on machines less than 100 KVA, the output power of the prime mover in KW may exceed the KVA rating of the generator. Although this may appear as a power factor of more than unity, it is always reported as unity for harmony with the accepted definition of power factor.
respectfully

 

[mottt]

no capacity curve.. i ask only if a old machine used to be similar to modern ones.... but, sorry for ask this questions...

thank in anyway for your reply and patience

 

[slavag]

Hi Motorxplosion.
It's so dificult to help you with this issue.
Not only dificult, it's also not correct from our,sorry, my side.
I'm hope, you understand what is your responsible
But let's try do something.
1. What is a type of earthing of stator point.
2. What is this gen:
Stanbay, work all time, what is a loads.
Are Connected directly to plant network or via trafo?
GE relay : I assume you will put SR489.
What is your CT, VT?
Are you have existing relays data?
I think you need start from very low settings and learn your optimal settings with time.
I will start from:
1. reverse power 32 on 2-3% Pnom to 10-15sec.
if you have signal like to "steam valve close" put additional short stage 3% Pnom for 3-4sec.
2. 46, NPS on 5-6% Inom 5sec Alarm and 8-10%Inom 10-12sec Trip.
Nominal of generator not CT, VT.
Thermal 49 maybe 105-110%Inom for 15-20min .
51 overcurrent first stage 120%Inom for 2-3sec
50 overcurrent stage 250-300%Inom for 0.15-0.25sec.
59 overvoltage 120% Unom for 0.3-0.5sec and 110%Unom for 5sec.
32Q or 40 or 55 need think about seetting, w/o gen data it's very difficult say.
Regards.
Slava

 

[slavag]

Sorry, Sorry.
I forgot, you wrote down, francis turbine.
I wrote down setting for function 32 as for steam turbine.
I don't know "typical setting" for francis or kaplan turbine.

 

[mottt]

thanks you very much slavag, i answer your questions,

the earthing of the stator is:
solid ground stator
The generator is a work all time one, and the load is connected to the net through a trafo.
yes, it´s a 489 relay, and the VT is 6600/110 and CT is 80/5-5.
thanks for your help...

 

[slavag]

Hi Motorxplosion.
Continue.
As I saied, I don't now "typical settings" for francis or kaplan turbine.
But, I don't see any problem put settings as for steam turbine, 2-3% for 10-12sec. ( of course w/o second short stage of 32)

I assume your generator are not main supply and you have
some connection from utilities.
Please send some schematic drw ( for this see FAQ faq238-1161).

For E/F protection I recommend add toroid CT on the grounding conductor of stator neutral point. Size you need choice according to SR489 parameters and settings
I think settings 6-8A primary for 0.5 sec and 12-15A primary for 0.1-0.2 sec are "not bad" for the begining.
Pay attention we don't take in account any setting coordination with others, we protect only on generator.
That means, possible trip from external faults, but I stay in this case: this generator is not main supply, I back it to work w/o any problem, I'm not utility, for me imortant generator.

Next one, we use on this moment only DT functionality, in next step you can use IDMT curves for 51, 46 ( O/C and NPS),
but for this size of generator I think it's not important.

I recommend also add V/Hz function and 81<> function.
1. V/Hz 112% for 4-5sec .
2. 105% and 95% of Fr nom for 2sec
Maybe in commissionig of AVR and protection will put this protections as alarms and after commissioning will connect to trip. These settings depend on your new AVR limit settings.

32Q or 40 it's a big problem. Try check what is old relay setting, and try translate old setting to new
You must two parameters of generator:
for offset Xd'- transient reactance of generator ( setting Xd'/2)
and for diametr Xd syn reactance of generator.
In your case, possible use some typical data for new generator.

Regards.
Slava